Android Room Database Ignore Problem “Tried the following constructors but they failed to match”

问题

My entity class:

@Entity(tableName = "student")
data class Student(
    var name: String,  
    var age: Int,   
    var gpa: Double,
    var isSingle: Boolean,

    @PrimaryKey(autoGenerate = true)
    var id: Long = 0,    

    @Ignore                           //don't create column in database, just for run time use
    var isSelected: Boolean = false                     
)

And then I insert like this (tested in androidTest):

val student = Student("Sam", 27, 3.5, true)

studentDao.insert(student)

It gives me this error right after I added the @Ignore annotation:

C:\Android Project\RoomTest\app\build\tmp\kapt3\stubs\debug\com\example\roomtest\database\Student.java:7: ����: Entities and POJOs must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).
public final class Student {
         ^
  Tried the following constructors but they failed to match:
  Student(java.lang.String,int,double,boolean,boolean,long) -> [param:name -> 
matched field:name, param:age -> matched field:age, param:gpa -> matched 
field:gpa, param:isSingle -> matched field:isSingle, param:isSelected -> 
matched field:unmatched, param:id -> matched field:id][WARN] Incremental 
annotation processing requested, but support is disabled because the 
following processors are not incremental: androidx.room.RoomProcessor 
(DYNAMIC).

回答1:

Since Room still generates Java-classes during compile and the problem is with default-valued parameter, try to use @JvmOverloads for constructor:

@Entity(tableName = "student")
data class Student @JvmOverloads constructor(
    var name: String,
    .....

UPDATE

It's interesting that here in documentation there is no mentioning of special treatment to this case. And this issue already exists to fix this documentation.

From this issue as for the problem itself conclusion is:

Using @JvmOverloads should work. One day in the not-so-distant future we might generate Kotlin and this won't be an issue

来源：https://stackoverflow.com/questions/64541459/android-room-database-ignore-problem-tried-the-following-constructors-but-they

标签

android

android-room

android-jetpack

android-database